1. Technical Field
The present invention relates to a nozzle plate and a droplet discharge head that are used in an inkjet head or the like, a method for manufacturing them, and a droplet discharge device.
2. Related Art
An inkjet head installed in an inkjet recording system generally includes a nozzle plate having a plurality of nozzle holes formed therein for discharging ink droplets, and a cavity plate having a discharge chamber bonded to the nozzle plate so as to communicate with the nozzle holes in the nozzle plate, and an ink flow path such as a reservoir. The inkjet head discharges an ink droplet from a selected nozzle hole by applying pressure to the discharge chamber from a driving section. Examples of driving systems include a system using an electrostatic force, a piezoelectric system using piezoelectric elements, and a system using heater elements.
In recent years, there has been an increasing demand for high quality in printing, images and the like. Therefore, high densification of nozzles and improvement in discharging performance have been attempted by arranging a plurality of nozzle rows, increasing the number of nozzles per row, extending the row of the nozzles, and so on. According to such a background, various innovations and suggestions have been made concerning a nozzle portion of the inkjet head.
For example, JP-A-56-135075 (FIG. 2) discloses forming a nozzle in a pyramid shape penetrating a silicon substrate having a (100) surface orientation by anisotropic wet etching.
JP-A-2006-45656 (FIGS. 4 and 16) discloses forming a nozzle in a tapered shape in a silicon substrate by alternately performing an isotropic dry etching and an anisotropic dry etching.
JP-A-10-315461 (FIGS. 1 and 2) discloses forming a tapered nozzle portion in a silicon substrate having a (100) surface orientation without penetrating, and then forming a perpendicular nozzle portion in a cylindrical shape penetrating the silicon substrate by anisotropic dry etching from the other surface of the silicon substrate.
JP-A-2000-203030 (FIG. 1) discloses forming an etch pit in a silicon substrate having a (110) surface orientation by anisotropic wet etching, and then forming a nozzle by anisotropic wet etching while the silicon substrate is soaked in an electrolyte solution and a reverse bias voltage is applied.
JP-A-11-28820 (FIGS. 3 and 4) discloses forming a nozzle having two stages in which a first nozzle portion in a cylindrical shape with a small diameter and a second nozzle portion in a cylindrical shape with a large diameter are formed in a silicon substrate having a (100) surface orientation by anisotropic dry etching.
However, techniques disclosed in JP-A-56-135075 (FIG. 2), JP-A-2006-45656 (FIGS. 4 and 16), JP-A-10-315461 (FIGS. 1 and 2), JP-A-2000-203030 (FIG. 1), and JP-A-11-28820 (FIGS. 3 and 4) described above have issues to be described below.
In JP-A-56-135075 (FIG. 2), since the nozzle is formed by anisotropic wet etching, an inclination angle of a tapered potion of the nozzle depends on a surface orientation of the silicon single crystal substrate. Therefore, increasing the nozzle density is limited. Further, an end of the nozzle becomes in a square shape due to the surface orientation of the silicon, making it hard to maintain a droplet straight flying property. Furthermore, since a discharge outlet of the nozzle does not have a perpendicular portion, it is hard to stably maintain a meniscus.
In JP-A-2006-45656 (FIGS. 4 and 16), undercuts in sidewalls of the nozzle proceed due to isotopic dry etching, causing difficulty in controlling a diameter of the nozzle. Further, since a discharge outlet of the nozzle does not have a perpendicular portion, it is hard to stably maintain a meniscus.
In JP-A-10-315461 (FIGS. 1 and 2), since the tapered nozzle portion is formed by anisotropic wet etching, an inclination angle of the tapered potion of the nozzle depends on a surface orientation of the silicon single crystal substrate. Therefore, increasing the nozzle density is limited. Further, since alignment of both sides of the tapered portion and the perpendicular portion of the nozzle is required, accuracy is inferior to a case where alignment is performed from one side to be processed.
In JP-A-2000-203030 (FIG. 1), since a tapered portion of the nozzle is formed by anisotropic wet etching, an inclination angle of the tapered potion of the nozzle depends on a surface orientation of the silicon single crystal substrate. Therefore, increasing the nozzle density is limited. Further, a border of the tapered portion and a perpendicular portion of the nozzle becomes indefinite, making it difficult to adjust a flow path resistance of the nozzle, that is, to adjust a length of the nozzle.
In JP-A-11-28820 (FIGS. 3 and 4), there is a stepped portion in a cylindrical shape between the first nozzle portion and the second nozzle portion, and thus stagnation of the ink flow occurs at the stepped portion, causing issues such as disturbance of flow and increase of a flow path resistance.